1 files changed, 12 insertions, 1 deletions
diff --git a/activerecord/lib/active_record/type/boolean.rb b/activerecord/lib/active_record/type/boolean.rb
index 06dd17ed28..978d16d524 100644
--- a/activerecord/lib/active_record/type/boolean.rb
+++ b/activerecord/lib/active_record/type/boolean.rb
@@ -10,8 +10,19 @@ module ActiveRecord
       def cast_value(value)
         if value == ''
           nil
+        elsif ConnectionAdapters::Column::TRUE_VALUES.include?(value)
+          true
         else
-          ConnectionAdapters::Column::TRUE_VALUES.include?(value)
+          if !ConnectionAdapters::Column::FALSE_VALUES.include?(value)
+            ActiveSupport::Deprecation.warn(<<-MSG.squish)
+              You attempted to assign a value which is not explicitly `true` or `false`
+              to a boolean column. Currently this value casts to `false`. This will
+              change to match Ruby's semantics, and will cast to `true` in Rails 5.
+              If you would like to maintain the current behavior, you should
+              explicitly handle the values you would like cast to `false`.
+            MSG
+          end
+          false
         end
       end
     end